LM139-N, LM239-N, LM2901-N, LM3302-N, LM339-N

SNOSBJ3E – NOVEMBER 1999 – REVISED DECEMBER 2014

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7 Detailed Description

7.1 Overview

The LM139/LM239/LM339 family of devices is a monolithic quad of independently functioning comparators

designed to meet the needs for a medium-speed, TTL compatible comparator for industrial applications. Since no

antisaturation clamps are used on the output such as a Baker clamp or other active circuitry, the output leakage

current in the OFF state is typically 0.1 nA. This makes the device ideal for system applications where it is

desired to switch a node to ground while leaving it totally unaffected in the OFF state. Other features include

single supply, low voltage operation with an input common mode range from ground up to approximately one volt

output supply to give switching levels from any voltage up to 36V down to a V CE SAT above ground

(approximately 100 mV), sinking currents up to 16 mA. The open collector output configuration allows the device

to be used in wired-OR configurations, such as a window comparators.

In addition it may be used as a single pole switch to ground, leaving the switched node unaffected while in the

OFF state. Power dissipation with all four comparators in the OFF state is typically 4 mW from a single 5-V

supply (1 mW/comparator).

7.2 Functional Block Diagram

7.3 Feature Description

The LMx39-N series are high-gain, wide bandwidth devices which, like most comparators, can easily oscillate if

the output lead is inadvertently allowed to capacitively couple to the inputs through stray capacitance. This shows

up only during the output voltage transition intervals as the comparator changes states. Reducing the input

resistors to < 10 k

Ω reduces the feedback signal levels and finally, adding even a small amount (1 to 10 mV) of

positive feedback (hysteresis) causes such a rapid transition that oscillations due to stray feedback are not

possible. Simply socketing the IC and attaching resistors to the pins will cause input-output oscillations during the

small transition intervals unless hysteresis is used. If the input signal is a pulse waveform, with relatively fast rise

and fall times, hysteresis is not required.

to prevent the input voltages from going negative more than

used as shown in the applications section.

The output of the LMx39-N series is the uncommitted collector of a grounded-emitter NPN output transistor.

Many collectors can be tied together to provide an output OR'ing function. An output pullup resistor can be

connected to any available power supply voltage within the permitted supply voltage range and there is no

package. The output can also be used as a simple SPST switch to ground (when a pullup resistor is not used).

10

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Product Folder Links: LM139-N LM239-N LM2901-N LM3302-N LM339-N